For Roofing

 Check flatness, slope and overhang of the frame on which the sheets are to be laid. Please remember that correcting the frame after laying the sheets will be difficult and at times impossible to rectify.

 Before lifting the sheets on to the roof, check if they are right side up.

 Place bundle of sheets over and near the firm supports and not at the mid-span of roof members.

 Sheets are normally laid from left to right commencing at Eaves, explained in
Figure-17  with sheets being numbered in order of fixing.

 The first sheet is laid at the Eaves, right angled (90 degrees) to the purlin with a side lap of one and a half corrugation.

  The minimum free overhang at Eaves must not exceed 300 mm. Care should be taken to ensure a minimum overhang of 100 mm at the side of the sheets. Ensure that the roofing sheets overhang minimum 50 mm into the Gutter at eave-end.

 It is considered good practice to use fasteners along side-laps of sheets.

  To be on the safe side, do not fix fasteners less than 25 mm from the end of the sheets. Maximum pitch between two fasteners, across the width of the sheet, should be 375 mm.

 While laying the first sheet at left of eave-end, please ensure that it is correctly located in relation to other parts of the building such as end and/or side-wall.

  Check alignment of sheets at repeated intervals. It is important to keep the gutter-end and ridge-end of all sheets in a straight line. This can be achieved by keeping the sheets parallel with respect to the first sheet.

  One can either fix each sheet completely before laying the next or can fix the sheet sufficiently to ensure it can't move, complete laying all sheets at one row and then return to place all intermediate fasteners.

  In Roof Cladding, for maximum water-tightness, fastening screws through the crest of the sheets on to the purlin is highly recommended. Always drive screws perpendicular to the sheet and at the centre of the corrugation. Placing screws on valleys may be susceptible to leakage in Roof Cladding.

The sheets on the next row are fixed similarly making an end lap (joint along the length of the sheet ) of minimum 150 mm.

  For Roof Cladding, allow a minimum end-lap of 200 mm for slopes of 5 to 14 degree, and 150 mm for slopes above 14 degree. For walls, allow minimum end lap of 100 mm.

  For slopes below 1 in 4 it is recommended to use sealant at the end lap with a minimum 3 mm bead of natural cure silicon sealant along the centre line of the fastener hole.

  Where four sheets meet at their corners, the total thickness becomes very thick. This gives a hump at the corners. To provide neat fit to the sheets at this junction any two corners of the diagonally opposite sheets have to be cut (mitred). Mitring means cutting of corners of the sheets to the measurement of side lap and end lap of the sheets.

  Care should be taken to ensure that the sheets do not butt against each other. The gap between each mitred corner should be approximately 2 mm. (The two diagonally mitred corners being covered by the uncut corners of the covering sheets will provide for perfect sealing against weather). Mitring should be done by carpenter's saw and sheets should never be chipped.

  At the ridge end of roofing, wind can push water up under the ridge, into the building. In order to arrest this problem, valleys of the sheets are bent upward at the ridge-end of roofing  (Figure-18) . This process blocks the valleys at ridge-end thereby preventing water from entering the building through ridge-end. This process is highly useful in roofs with slopes below 1 in 2 (25°). In contrast, valleys at the
eave-end of roofing sheet are bent down in order to achieve enhanced weatherproofing and smooth flow of water
into the Gutters. Bending of sheets at valleys can be done with the help of multi-grip pliers or a sliding spanner.

For Wall Cladding

In Wall Cladding fasteners are usually placed in the valley of the sheets since water penetration is not a problem in Wall Cladding. Fasteners at valleys are less noticeable and do not affect the aesthetic of the Steel Cladding. Also fasteners fixed on valleys of Wall Cladding minimize the risk of deformation of profile since the fastener rests flat against its support, i.e. Side Girt .
However, when valley-fixed, the cladding needs a side-lap fastener in all laps, in order to hold the profiles of two sheets together   (Figure-19).

CONDENSATION & HEAT CONTROL

When the air in a building in contact with metal cladding is warmer than the cladding, moisture in the air can condense on the inside of cladding. Condensation can lead to deterioration of building components, staining of ceiling & walls and even deterioration of items stocked inside the stocking area. The amount of condensation depends upon the amount of moisture present in the air and this varies with climatic conditions. Activities within a building such as washing and drying of clothes, cooking, showering etc. may add substantially to the amount of moisture in the air. In the event of extreme moisture content inside the building, it is essential to either keep cladding away from moist atmosphere inside the building or vent substantial amount of air moisture to the outside of the building.